Adaptation of an artificial bait to an automated aerial delivery system for landscape-scale brown treesnake suppression

Abstract

Dead neonatal mice are currently used as bait for delivery of toxin to invasive brown treesnakes (Boiga irregularis) on Guam; once deployed in the field the mice are highly attractive to the snakes but only for about four days. An artificial bait containing a mixture of fats mimicking those in skin of the mice is also highly attractive to the snakes and remains attractive 2–3 times longer. The artificial bait, however, costs more than the mice, and is more difficult to attach to the capsules of a novel aerial bait delivery system. This paper describes a reformulation of the bait which reduced the ingredient cost to 11% of its former value, without compromising its attractiveness to free-ranging snakes. Three lipid formulations using different source materials to produce the same fatty acid profile target were tested along with two levels of pork fat to yield six test formulations. No differences in bait disappearance were noted in field testing of the baits, indicating that decisions regarding bait formulation could be made on the basis of cost without sacrificing efficacy. Separately, testing of 17 commercially available adhesives identified five for field testing. Among these, two demonstrated strong, weather-resistant bonds between the oily surface of the artificial baits and the bait capsules as evidenced by only 13.4% and 4.5% of baits falling off suspended capsules. Importantly, neither of these adhesives impacted bait removal by snakes in field trials in comparison to baits with no adhesive.. The results represent an advance in technology development for landscape-scale suppression of brown treesnake populations.